1. Field of the Invention
The present invention relates to an electric circuit device having a chip mounted in a face-down orientation on a circuit board. Here, the term "chip" refers to any electrical component, such as, but not limited to, components having rectangular casings.
2. Description of the Related Art
FIG. 1 illustrates a related method employed when a chip 2 is mounted on a circuit board 1, such as a printed circuit board or the like. The circuit board is formed using an epoxy resin or the like as a base material. A hybrid integrated circuit can be formed on the circuit board using the so-called "solder bump" technique. More particularly, a chip 2 is mounted in a face-down orientation by bonding the solder bumps 4 of the chip 2 to an electrode 3 formed on the circuit board 1. The electrode 3 of the circuit board 1 is coated with a solder resist film 5 so that the solder resist film 5 prevents a solder from wetting and unnecessarily spreading on the electrode 3 when the solder is applied. After the solder bumps 4 are bonded as described above, the board is cleaned by removing the flux. A sealing resin 6 is discharged to the chip 2 on one side end of the chip, or near one side or two sides of the chip by means of a dispenser 7 or the like. The solder then flows into the gap between the chip 2 and the circuit board 1 based on the capillary phenomena. Then, the resin is heat-cured or photo-cured for making a seal with the resin (see FIG. 2). In FIGS. 1 and 2, just the chip 2 is mounted on the circuit board 1 for ease of illustration. However, other surface mounted components such as chip capacitors, chip resistors, and the like can be mounted adjacent to the chip 2.
In the hybrid integrated circuit as described above, the resin 6 becomes a smooth fillet 6a due to its surface tension. The fillet 6a bulges outward from the chip 2. When the board 1 is heated, or the resin 6 having a low viscosity is used to enhance the flow of the resin 6, the surface tension of the resin 6 decreases. As a result, the fillet 6a can enlarge and spread out, or the resin 6 is formed into a pseudo-circular shape at the location where the resin was initially discharged from the dispenser. This is an undesirable shape for resin sealing. Further, in some cases, variations in the discharge quantity of the resin from the dispenser 7 cause the fillet to become enlarged. When the resin 6 is considerably spread outward from the chip 2, as described above, the resin 6 may cover the electrode surface on which a component is to be mounted. This causes problems because the electrical connection is impaired. Also, the danger of the resin spreading hinders producing a device having high mounting density.